Protein Kinases (PKs) are enzymes that catalyze the phosphorylation of hydroxyl groups on tyrosine, serine and threonine residues of proteins. The phosphorylation of proteins modulates various cell activities such as cell growth, differentiation and proliferation. Abnormal PK activity has been linked to a host of disorders, ranging from relatively non-life threatening diseases such as psorisasis to extremely virulent diseases such as glioblastoma (brain cancer).
A great deal of effort has been expended in an attempt to identify ways to modulate PK activity. Examples are: biomimetic approaches using large molecules patterned on those involved in the actual cellular processes (e.g., mutant ligands (U.S. Pat. No. 4,966,849); soluble receptors and antibodies (WO 94/10202, Kendall et al., Proc. Nat'l Acad. Sci., 90: 10705-09 (1994), Kim et al., Nature, 362: 841-844 (1993)); RNA ligands (Jelinek et al., Biochemistry, 33: 10450-56); Takano et al., Mol. Bio. Cell, 4: 358A (1993); Kinsella et al., Exo. Cell Res., 199: 56-62 (1992); Wright et al., J. Cellular Phys., 152: 448-57); and tyrosine kinase inhibitors (WO 94/03427; WO 92/21660; WO 91/15495; WO 94/14808; U.S. Pat. No. 5,330,992; Mariani et al., Proc. Am. Assoc. Cancer Res., 35: 2268 (1994)). Despite such attempts, a need still exists for effective methods of modulating PK activity.